U.S. patent number 4,908,331 [Application Number 07/369,443] was granted by the patent office on 1990-03-13 for method of manufacturing a semiconductor device by depositing metal on semiconductor maintained at temperature to form silicide.
This patent grant is currently assigned to U.S. Philips Corporation. Invention is credited to Ivo J. M. M. Raaijmakers.
United States Patent |
4,908,331 |
Raaijmakers |
March 13, 1990 |
Method of manufacturing a semiconductor device by depositing metal
on semiconductor maintained at temperature to form silicide
Abstract
A method of manufacturing a semiconductor device comprises a
semiconductor body (1) having a surface (2), which is adjoined by
regions of silicon (3, 4, 5 and 6) and regions of insulating
material (8 and 9), the regions of silicon being provided with a
top layer (10) of a metal silicide by depositing metal on the
surface while heating the semiconductor body to a temperature at
which metal silicide is formed during the deposition. According to
the invention, cobalt or nickel is deposited while the
semiconductor body is heated to a temperature at which cobalt or
nickel silicide is formed. Thus, metal silicide does not grow over
parts of the regions of insulating material adjoining directly the
regions of silicon.
Inventors: |
Raaijmakers; Ivo J. M. M. (San
Jose, CA) |
Assignee: |
U.S. Philips Corporation (New
York, NY)
|
Family
ID: |
19852533 |
Appl.
No.: |
07/369,443 |
Filed: |
June 21, 1989 |
Foreign Application Priority Data
|
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|
|
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Jun 27, 1988 [NL] |
|
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8801632 |
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Current U.S.
Class: |
438/682;
257/E21.165; 257/E21.586; 438/664; 438/674 |
Current CPC
Class: |
H01L
21/28518 (20130101); H01L 21/76879 (20130101) |
Current International
Class: |
H01L
21/02 (20060101); H01L 21/285 (20060101); H01L
21/70 (20060101); H01L 21/768 (20060101); H01L
021/285 (); H01L 029/54 (); H01L 029/62 () |
Field of
Search: |
;437/187,200
;148/DIG.147 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Gross et al., J. Vac. Sci. Techol., B, 6(5), pp. 1548-1552. .
West et al., Appl. Phys. Lett., 53(9)., pp. 740-742. .
Gross et al., Proc. Electrochem. Soc., 87-88 (Proc. Int. Conf.
Chem. Vapor Deposition, 10th, 1987), pp. 759-765. .
Murarka et al., J. Appl. Phys., vol. 56, No. 12 (Dec. 1984), pp.
3404-3412..
|
Primary Examiner: Chaudhuri; Olik
Attorney, Agent or Firm: Miller; Paul R.
Claims
I claim:
1. A method of manufacturing a semiconductor device comprising a
semiconductor body having a surface which is adjoined by regions of
silicon and regions of insulating material, the regions of silicon
being provided with a top layer of a metal silicide by depositing
metal on the surface and heating the semiconductor body to a
temperature at which the metal silicide is formed during the
deposition by reaction of the metal with the silicon, characterized
in that a metal cobalt or nickel is deposited on the surface, while
maintaining the semiconductor body at a temperature at which cobalt
or nickel disilicide is formed.
2. A method as claimed in claim 1, characterized in that said metal
is cobalt.
3. A method as claimed in claim 2, characterized in that the
semiconductor body is heated during the deposition of cobalt to a
temperature which lies between 500.degree. C. and 800.degree.
C.
4. A method as claimed in claim 3, characterized in that the
semiconductor body is heated during the deposition of cobalt to a
temperature which lies between 580.degree. C. and 660.degree.
C.
5. A method as claimed in claim 1, characterized in that the
semiconductor body is heated during the deposition of nickel to a
temperature which lies between 750.degree. C. and 900.degree.
C.
6. A method as claimed in claim 5, characterized in that the
semiconductor body is heated during the deposition of nickel to a
temperature which lies between 800.degree. C. and 880.degree.
C.
7. A method as claimed in claim 1, characterized in that the
surface is cleaned before the metal deposition by carrying out a
sputter etching treatment, and in that then the metal deposition is
carried out directly without exposing the surface to air.
Description
The invention relates to a method of manufacturing a semiconductor
device comprising a semiconductor body having a surface adjoined by
regions of silicon and regions of insulating material, the regions
of silicon being provided with a top layer of a metal silicide by
depositing metal on the surface and by then heating the
semiconductor body to a temperature at which during the deposition
the metal silicide is formed by reaction of the metal with the
silicon.
The regions of silicon may be both regions of monocrystalline
silicon and regions of polycrystalline silicon. In the first case,
they constitute, for example, semiconductor zones of transistors,
such as source and drain zones of field effect transistors; in the
second case, they constitute, for example, conductor tracks, such
as gate electrodes of field effect transistors. Both kinds of
regions of silicon may of course also form past of bipolar
transistors and of other semiconductor circuit elements. The
regions of insulating material may mutually insulate as field oxide
regions circuit elements provided in the semiconductor body. They
may also constitute, for example, an insulation between gate
electrodes and source and drain zones of field effect transistors.
They may be made of different materials, such as silicon oxide,
silicon nitride, silicon oxynitride, but also, for example, of
aluminum oxide.
By providing the silicon regions with a top layer of a metal
silicide, it is achieved inter alia that monocrystalline
semiconductor zones can be more readily contacted and that
polycrystalline conductor tracks obtain a lower electrical
resistance. The regions are provided in the manner described above
in a self-registered manner with a top layer of a metal silicide.
During the deposition, the metal reacts with silicon, but it will
not react with the insulating material. After deposition, the metal
can be simply etched away from the regions of insulating material,
while the metal silicide is left behind as a top layer on the
silicon regions.
U.S. Pat. No. 4,526,665 discloses a method of the kind mentioned in
the opening paragraph, in which as metal titanium, tantalum,
molybdenum, niobium or tungsten is deposited on the surface. The
semiconductor body is then heated to a temperature lying between
450.degree. C. and 650.degree. C.
A disadvantage of the known method is that during the metal
deposition a silicide is formed not only on the regions of silicon,
but also on parts of the regions of insulating material directly
adjoining the regions of silicon. Such a growth of metal silicide
over parts of insulating material can give rise to short-circuits,
especially if the regions of insulating material have very small
dimensions of, for example, less than 1 .mu.m.
The invention has inter alia for its object to provide a method,
which permits providing the silicon regions with a top layer of a
metal silicide, the overgrowth of metal silicide on the regions of
insulating material being practically avoided.
For this purpose, according to the invention, the method mentioned
in the opening paragraph is characterized in that, as a metal
cobalt or nickel, is deposited on the surface, while the
semiconductor body is then heated to a temperature at which cobalt
or nickel disilicide is formed.
The invention is based on the recognition of the fact that growth
of metal silicide over parts of the regions of insulating material
directly adjoining the silicon regions using one of the metals
titanium, tantalum, molybdenum, niobium or tungsten (as are used in
the known method described) is due to two causes. A first cause
resides in the fact that the metal silicide of the metals has a
larger molar volume than that of silicon. The metal silicide
effectively grows from the regions of silicon and then over the
regions of insulating material. A second cause resides in the fact
that during the formation of the metal silicide silicon atoms
diffuse more rapidly through the metal silicide than the atoms of
the metals. This means that during the growth of the top layer of
metal silicide silicon atoms diffuse through the metal silicide and
then react with metal atoms. Since such a diffusion occurs
especially in a lateral direction, i.e. in the direction of the
regions of insulating material, metal silicide can be formed also
on these regions.
According to the invention cobalt or nickel disilicide is formed.
These disilicides have a molar volume which is smaller than that of
silicon. As a result, the metal silicide effectively grows into the
regions of silicon. Moreover, the semiconductor body is heated
during the metal deposition to a temperature at which cobalt or
nickel disilicide is directly formed. In this case, silicon atoms
diffuse even more slowly during the growth of the metal silicide
through metal silicide than the metal atoms. This also results in
that it is counteracted that metal silicide is formed on the
regions of insulating material.
It should be noted that during the formation of cobalt or nickel
monosilicide silicon atoms diffuse more rapidly through the metal
silicide than the metal atoms. This form of metal silicide is not
obtained, however, if during the deposition the temperature of the
semiconductor body is sufficiently high. In this case, disilicide
is formed directly. Cobalt disilicide is formed directly if the
temperature of the semiconductor body is higher during the metal
deposition than 500.degree. C. While nickel disilicide is formed
directly if this temperature is higher than 750.degree. C.
Since cobalt disilicide has a considerably lower resistivity than
nickel disilicide, metal cobalt is preferably deposited on the
surface of the semiconductor body.
Preferably, the semiconductor body is heated during the deposition
of cobalt to a temperature which lies between 500.degree. C. and
800.degree. C. Below 500.degree. C., there is a risk that instead
of disilicide monosilicide is formed. Above 800.degree. C. there is
a risk that in the presence of cobalt the regions of insulating
material change in structure in such a manner that, after cobalt
has been etched away, an insulating layer having a rough surface is
left. If cobalt is deposited at too high a deposition rate, the
undesired monosilicide is formed. If cobalt is deposited at a
suitable deposition rate, this is not the case. If the
semiconductor body is heated to a temperature of 580.degree. C., no
monosilicide is formed if cobalt is deposited at a rate of about 1
nm/sec; if the temperature is 620.degree. C. at a deposition rate
of about 5 nm/sec and if the temperature is 650.degree. C. at a
deposition rate of about 10 nm/sec, this is not the case either.
Preferably, the semiconductor body is heated to a temperature lying
in this temperature range because a practical deposition rate can
then be chosen. In practice a layer of cobalt disilicide of about
60 nm is necessary (the electrical resistance is then about 3 Ohms
per square), for which about 20 nm of cobalt must be deposited.
This can then take place within about 2 to 20 seconds.
The invention will now be described more fully with reference to a
drawing. In the drawing:
FIGS. 1 and 2 show two stages of manufacture of a semiconductor
device, which is obtained by means of the method according to the
invention.
The semiconductor device comprises a semiconductor body 1 having a
surface 2, which is adjoined by regions of silicon 3, 4, 5 and 6
and regions of an insulating material 8 and 9. The regions of
silicon 3, 4 and 5 consists of monocrystalline silicon. The regions
3 and 4 constitute in this embodiment the source and drain zones of
a field effect transistor. Via the region 5, for example, the
semiconductor body 1 may be contacted. The region of silicon 6
consists of polycrystalline silicon and constitutes the gate
electrode of the field effect transistor, which is insulated by a
layer of gate oxide 7 from the part of the semiconductor body 1
located between the source zone and the drain zone 3 and 4,
respectively. The regions of insulating material 8 and 9 in this
embodiment consists of silicon oxide, but they may also consists of
silicon nitride, silicon oxynitride or even of aluminium oxide. The
insulating regions 8 insulate as field oxide regions the source and
drain zones 3, 4 from the region 5. The insulating regions 9
insulate the gate electrode 6 in lateral direction from the source
and drain zones 3 and 4.
The regions of silicon 3, 4, 5 and 6 are provided with a top layer
10 of a metal silicide by depositing metal on the surface 2 and by
then heating the semiconductor body 1 to a temperature at which the
metal silicide 10 is formed during the deposition by reaction of
the metal with the silicon 3, 4, 5 and 6. The monocrystalline
silicon regions 3, 4 and 5 can thus be contacted more
satisfactorily and the polycrystalline silicon region 6 thus has a
lower electrical resistance.
The silicon regions 3, 4, 5 and 6 are provided in a self-registered
manner with the top layer 10. During the deposition, the metal
reacts with silicon, but this will not be the case with the
insulating material of the regions 8 and 9. After the top layer 10
has been formed, the metal which has been deposited on the
insulating regions 8 and 9 can be simply etched away in a usual
manner selectively with respect to the metal silicide formed.
According to the invention, metal cobalt or nickel is deposited on
the surface 2, while the semiconductor body 1 is then heated to a
temperature at which cobalt or nickel disilicide is formed. Due to
the measure according to the invention, the formation of metal
silicide on parts of the regions of insulating material 8 and 9,
which immediately adjoin the regions of silicon 3, 4, 5 and 6, is
practically avoided. Since both cobalt and nickel disilicide have a
molar volume (of 38.6.times.10.sup.-3 nm.sup.3 and
39.3.times.10.sup.-3 nm.sup.3, respectively) which is smaller than
that of two silicon atoms (of 40.0.times.10.sup.-3 nm.sup.3), the
metal silicide effectively grows into the regions of silicon 3, 4,
5 and 6. Moreover, the semiconductor body 1 is heated during the
metal deposition to a temperature at which cobalt or nickel
disilicide is formed. During the growth of the metal silicide,
silicon atoms diffuse more slowly than metal atoms through metal
silicide. The growth of the metal silicide therefore takes place
mainly near the transition between silicon and metal silicide. Also
as a result thereof, the formation of metal silicide on the regions
of insulating material 8 and 9 is counteracted. In practice, it has
been found that no cobalt or nickel disilicide is formed on the
regions of insulating material 8 and 9.
Cobalt and nickel may be deposited in a usual manner, for example
by means of magnetron sputtering or evaporation, on a semiconductor
body. In the second case, the metal is then preferably heated by
means of an electron beam.
Preferably, the semiconductor body 1 is heated during the
deposition of cobalt to a temperature lying between 500.degree. C.
and 800.degree. C. Below 500.degree. C., monosilicide is formed,
while above 800.degree. C. there is a risk that in the presence of
cobalt the regions of insulating material 8, 9 degrade to such an
extent that, after cobalt has been etched away, an insulating layer
having a rough surface is left. During the deposition of nickel,
for the same reasons the semiconductor body is preferably heated to
a temperature lying between 750.degree. C. and 900.degree. C.
During the growth of cobalt and nickel disilicide, diffusion of
metal atoms through silicide already formed plays an important
part. If the metal atoms are deposited at too high a rate, the
undesired monosilicide is formed. Through monosilicide, silicon
atoms diffuse more rapidly than metal atoms so that there is a risk
that overgrowth of silicide on insulating material occurs. This
risk does not exist if before the formation of cobalt disilicide
the semiconductor body is heated to a temperature of 580.degree.
C., 620.degree. C. and 660.degree. C. and if cobalt is then
deposited at a rate of 1 nm/sec, 5 nm/sec and 10 nm/sec,
respectively. These rates are practical deposition rates at which a
layer of cobalt of about 20 nm can be deposited in 2 to 20 seconds.
A layer of cobalt disilicide of about 60 nm is then formed having a
resistance of about 3 Ohms per square. A layer of nickel disilicide
must be about 3 times thicker in order to obtain the same low
resistance. In order that such a layer can also be deposited in 2
to 20 seconds without the likewise undesired nickel monosilicide
being formed, the semiconductor body must then be heated to a
temperature which lies between 800.degree. C. and 880.degree. C. At
800.degree. C., nickel can then be deposited at a deposition rate
of about 2 nm/sec, at 840.degree. C. at a rate of about 10 nm/sec,
at 880.degree. C. at a rate of about 20 nm/sec.
Preferably, as metal cobalt is deposited on the semiconductor
surface because cobalt disilicide has a lower resistivity than
nickel disilicide (18 and 50 .mu..OMEGA.-cm, respectively) so that,
in order to obtain a layer of metal silicide having a desired
resistance per square, the quantity of cobalt to be deposited is
smaller than that of nickel.
If the surface 2 is thoroughly cleaned before the metal deposition,
preferably by carrying out a usual sputter etching treatment, after
which cobalt or nickel is deposited in the same apparatus directly
without exposing the surface to air, the layer grows epitaxially
and a monocrystalline layer of disilicide is formed on the
monocrystalline silicon regions 3, 4 and 5. Such a monocrystalline
layer of disilicide may be used, for example, for manufacturing a
socalled metal-base transistor.
* * * * *